Noise Figure Reduction Research Articles

Performance Enhancement of the nMOSFET Low-Noise Amplifier by Package Strain

The package strain improves the noise figure (NF) of the low-noise amplifier (LNA). The maximum noise reduction is ~0.53 dB (13%) at the operating frequency of 2.4 GHz under the biaxial tensile strain of 0.037%. The NF reduction of the strained LNA is mainly due to the enhanced transconductance and cutoff frequency of the individual nMOSFET device under the same strain and bias conditions

Microwave Photonic Link with Carrier Suppression for Increased Dynamic Range

Theoretical analysis and experimental investigation of microwave photonic links with bias-shifted Mach-Zehnder modulators are presented. An optical amplifier is used to increase link gain and reduce noise figure. The combination of modulator bias shift away from quadrature and optical amplification reduces the link noise figure by more than 15 dB. For modulation frequencies from 2 to 18 GHz, the third-order limited spurious-free dynamic range (SFDR3) of these links is greater than 120 dB, normalized to a 1-Hz bandwidth. Conventional links based on Mach-Zehnder modulators are limited to SFDR3 values of approximately 110 dB, normalized to a 1-Hz bandwidth. This level of performance is achieved without electronic or optical linearization.

Effect of gate-drain/source overlap on the noise in 90nm N-channel metal oxide semiconductor field effect transistors

In this paper, we have studied the effect of gate-drain/source overlap (LOV) on the drain channel noise and induced gate current noise (SIg) in 90nm N-channel metal oxide semiconductor field effect transistors using process and device simulations. As the change in overlap affects the gate tunneling leakage current, its effect on shot noise component of SIg has been taken into consideration. It has been shown that “control over LOV” allows us to get better noise performance from the device, i.e., it allows us to reduce noise figure, for a given leakage current constraint. LOV in the range of 0–10nm is recommended for the 90nm gate length transistors, in order to get the best performance in radio frequency applications.

An ultralow-loss and broadband micromachined RF inductor for RFIC input-matching applications

In this brief, we demonstrate that ultralow-loss and broadband inductors can be obtained by using the CMOS process compatible backside inductively coupled-plasma (ICP) deep-trench technology to selectively remove the silicon underneath the inductors. The results show that a 378.5% increase in maximum Q-factor (Q/sub max/) (from 10.7 at 4.7 GHz to 51.2 at 14.9 GHz), a 22.1% increase in self-resonant frequency (f/sub SR/) (from 16.5 to 20.15 GHz), a 16.3% increase (from 0.86 to 0.9999) in maximum available power gain (G/sub Amax/) at 5 GHz, and a 0.654-dB reduction (from 0.654 dB to 4.08/spl times/10/sup -4/ dB) in minimum noise figure (NF/sub min/) at 5 GHz were achieved for a 2-nH inductor after the backside ICP dry etching. In addition, state-of-the-art ultralow-loss G/sub Amax//spl les/0.99 (i.e., NF/sub min//spl les/0.045 dB) for frequencies lower than 12.5 GHz was achieved for this 2-nH inductor after the backside inductively coupled-plasma dry etching. This means this on-chip inductor-on-air can be used to realize an ultralow-noise 3.1-10.6 GHz ultrawide-band RFIC. These results show that the CMOS process compatible backside ICP etching technique is very promising for system-on-a-chip applications.

Effects of layout methods of RFCMOS on noise performance

This paper presents a study on the effects of different layout methods on the noise performance of RF CMOS transistors. The optimization of RF characteristics using multifinger layout and a more compact waffle layout with Manhattan-oriented polysilicon gate are studied. The waffle layout is demonstrated to have a larger design window through the simulation as well as the experimental data. The improvement of both the maximum oscillation frequency f/sub max/ and the cutoff frequency f/sub T/ at the same biasing condition leads to the improvement on RF noise performance for the waffle MOSFETs. Compared with the multifinger devices, the SpectreRF simulation reveals that 10% reduction in noise figure is achieved when the waffle MOSFETs are used in CMOS low-noise amplifiers.

Characterization of a Low-Noise Linearized Microwave Power Amplifier Module

An X-band, low-noise, linearized microwave power amplifier module consisting of a low-noise solid-state amplifier (SSA), predistortion linearizing circuit, and low-gain helix traveling wave tube (TWT) is designed and tested in order to demonstrate both reduced noise figure and suppressed intermodulation distortion ratio. Two-tone intermodulation distortion (IMD) ratios are predicted from simulations obtained from modeling of the TWT, linearizing circuit, and SSA by the use of Agilent's Advanced Design System simulation code. Simulated IMD ratios are in good agreement with measured results. Measurements show a noise figure of 2.2 dB at 9.5 GHz and the third-order IMD ratio of -53 dBc at 10 dB input back off from the input P1dB point. It is found that both noise figure and IMD ratio are significantly improved compared with conventional helix-TWTs and microwave power modules.

A 2.17-dB NF 5-GHz-band monolithic CMOS LNA with 10-mW DC power consumption

Design principles of CMOS low-noise amplifiers (LNAs) for simultaneous input impedance and noise matching by tailoring device size for R/sub opt/=50 /spl Omega/ are introduced. It is found that R/sub opt/ close to 50 /spl Omega/ can be obtained by using small devices (110 /spl mu/m) and small currents (5 mA). Based on the proposed approach, CMOS LNAs with on-chip input and output matching networks on thin (/spl sim/20 /spl mu/m) and normal (750 /spl mu/m) substrates are implemented. It is found that the noise figure (NF) (3.0 dB) of the CMOS LNA at 5.2 GHz with 10-mW power consumption on the normal (750 /spl mu/m) substrate can be reduced to 2.17 dB after the substrate is thinned down to /spl sim/20 /spl mu/m. The reduction of NF is attributed to the suppression of substrate loss of the on-chip inductors. The input return loss (S/sub 11/) is smaller than -22 dB across the entire band of interest (5.15-5.35 GHz). An input 1-dB compression point (P/sub 1 dB/) of -8.3 dBm and an input third-order intercept point of 0.8 dBm were also obtained for the LNA on the thin substrate.

Novel long-period fiber gratings written by high-frequency CO 2 laser pulses and applications in optical fiber communication

In this paper, we report novel long-period fiber gratings (LPFGs) fabricated by using a new writing technique that is mainly based on the thermal shock effect of focused high-frequency CO 2 laser pulses at several kHz. Several unique characteristics of these LPFGs, such as bend and transverse-load, etc., are observed by experiments, for the first time, to our knowledge. These unique features of the LPFGs are mainly due to the asymmetrical distribution of the refractive index on the cross-section of the LPFG induced by high-frequency CO 2 laser pulses. Based on these novel LPFGs, an amplified spontaneous emission noise filter and a gain equalizer have been demonstrated for the noise figure reduction and the gain spectrum flattening of Er-doped fiber amplifiers (EDFAs), respectively. By means of the unique bending and loading features of the LPFG, two tunable gain equalizers have been demonstrated for dynamic gain flattening of EDFAs.

Influence of unpumped EDF position and auxiliary pump wavelength on L‐band EDFA performance

AbstractLarge gain enhancement in a novel long‐wavelength band (L‐band) erbium‐doped fiber amplifier (EDFA) is demonstrated by the cascade of pumped and unpumped erbium‐doped fibers. By utilizing an injected conventional wavelength band (C‐band) laser as an auxiliary pump signal, an approximately 7.5‐dB gain improvement is achieved. The EDFA performances are analyzed and explained in terms of C‐band wavelength, and pumped and unpumped erbium‐doped fiber sequence. The results indicate that there is a tradeoff between gain enhancement and noise figure reduction. © 2003 Wiley Periodicals, Inc. Microwave Opt Technol Lett 37: 95–98, 2003; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/mop.10834

Gain and Noise Figure Improvements in Double Pass L-band EDFA using a Band-pass Filter

A new double pass long wavelength band erbium-doped fiber amplifier (L-band EDFA) configuration with improved gain and noise figure is demonstrated by placing a band-pass filter in the output end of the erbium-doped fibre (EDF). Compared to the previous double pass amplifier, the proposed amplifier provides a maximum gain enhancement of 1.5 dB with reduction of noise figure by 1.2 dB at a pump power of 83 mW.

Reduction of Raman MPI and noise figure in dispersion-managed fibre

Raman amplification in dispersion-managed fibre is studied experimentally. In positive-dispersion (+D)/inverse-dispersion (-D) configuration, severe multipath interference impairments at high Raman gain are observed. These are eliminated by using the +D/-D/+D configuration. In addition, the Raman gain in the +D/-D/+D configuration starts earlier in the span, improving the noise figure dramatically over conventional transmission fibres.

Noise Figure Reduction in Erbium-Doped Fiber Amplifiers Using Loop Mirror Filter

Noise figure reduction of an erbium-doped fiber amplifier using loop mirror filter is demonstrated. Approximately 0.5-dB noise figure reduction is achieved at input signal power level below - 30dBm. Transferring energy from the amplifier spontaneous emission to the input signal compensates for the insertion loss of the loop mirror filter device. The insertion loss of the device approximately 1 dB.

Noise Figure Reduction in Erbium-Doped Fiber Amplifiers Using Loop Mirror Filter

Noise figure reduction of an erbium-doped fiber amplifier using loop mirror filter is demonstrated. Approximately 0.5-dB noise figure reduction is achieved at input signal power level below - 30dBm. Transferring energy from the amplifier spontaneous emission to the input signal compensates for the insertion loss of the loop mirror filter device. The insertion loss of the device approximately 1 dB.

Noise analysis of conventional and gain-clamped semiconductor optical amplifiers

We present a numerical study of the noise of conventional and gain-clamped semiconductor optical amplifiers (SOAs), using a detailed device model. The model makes use of a density-matrix gain calculation, and takes into account the forward and backward amplified spontaneous emission (ASE) spectra and the spatial carrier hole-burning. The device is longitudinally divided into M sections and a rate equation for averaged photon and carrier densities is used for each section. We demonstrate that the accuracy on the calculated noise figure strictly depends on the number of sections M. We obtain a good tradeoff between the results accuracy and the computational complexity with M=8. The model is then applied to study the noise in a distributed Bragg reflector (DBR)-type gain-clamped SOA for varying signal power, pump current, and lasing wavelength. We show that changes in the spatial carrier profile caused by the input signal significantly affect the noise figure, even when the gain is constant. A slight dependence of the noise figure on lasing wavelength is also foreseen, while the dependence on the pump current is negligible. A new method for gain-clamped SOA noise figure reduction is proposed, based on unbalanced Bragg reflectors. An improvement of noise figure (NF) as large as 2 dB is devised.

Comments on "Optical amplifier noise figure reduction for optical single-sideband signals"

In a recent paper (see Proc. Inst. Radio Eng., vol.32, p.419, 1944). it was demonstrated that a noise figure below the so-called quantum limit is possible using single-sideband (SSB) modulation. In this comment we discuss the interpretation of this result and its implications for optical communications systems.

Optimum configuration for high-power low-noise-figure erbium-doped fiber amplifiers for lightwave CATV applications

We theoretically investigate various 980-nm-pumping configurations for simultaneously achieving high-power, low-noise-figure erbium-doped fiber amplifiers (EDFAs) acted as power amplifiers and in-line amplifiers for lightwave analog cable-television (CATV) applications. The target of saturated output power and noise figure is ≥100 mW and ≤5 dB, respectively. Those configurations considered include single-stage and two-stage designs in dual-forward, dual-backward, and bidirectional pumping schemes, each with and without the midway optical isolator. The bidirectional pumping scheme includes the forward-and-backward, and the backward-and-forward cases. A total of nine configurations are examined and compared in this paper. We find that the midway isolator for all amplifier configurations operated at large input signal level (>0 dBm) in CATV analog systems did not contribute to noise figure reduction, but the additional insertion loss reduced the output power. This is quite opposite to the case for an amplifier operated at small input signal power in the digital systems. From both system power budget and carrier-to-noise ratio (CNR) points of view, among all configurations, the single-staged forward-and-backward bidirectional pumping scheme without using inter-staged components is the best amplifier configuration to offer the highest output power with fairly low noise figure and highly satisfied CNR performance. It is also the simplest scheme with the shortest required EDF length. This conclusion provides the configuration selection of designing both power and in-line amplifiers for AM CATV lightwave systems.

Optical amplifier noise figure reduction for optical single-sideband signals

This paper analyzes the amplification of optical single-sideband signals, highlighting the significance of the optical signal bandwidth in determining signal-amplified spontaneous emission (ASE) beat noise. It predicts that an electrical noise figure of one may be realized for single-sideband signals using appropriate optical filtering. It verifies noise figure reduction experimentally, demonstrating an electrical noise figure of 1.1/spl times/ the spontaneous emission factor of the amplifier, which is 2.6 dB below the limit for conventional intensity modulated signals.

Improvement of gain and noise figure by periodic bending of an erbium-doped fiber

The gain and noise figure can be improved by periodic bending of an erbium-doped fiber. Bending of 5.4 m at the beginning of an erbium-doped fiber results in a reduction of noise figure, a gain increment, and a reduction of forward amplified spontaneous emission of 5.1, 3.6, and 1.5 dB for a 1533-nm small signal; 4.0, 1.9, and 2.1 dB for a 1550-nm small signal; and 2.7, 0.9, and 1.8 dB for a 1560-nm small signal (-40 dBm), respectively. In addition, the periodic bending can operate an erbium-doped fiber amplifier at quantum-limited noise and enables its operation to be more stable.

A monolithic HEMT-HBT direct-coupled amplifier with active input matching

We have achieved the first active input matching of a monolithic microwave integrated circuit through the use of a common-gate (CG) HEMT directly coupled to the input of an HBT Darlington feedback amplifier. The HEMT and HBT devices were monolithically integrated on the same chip using selective MBE. This circuit features an active impedance match technique that eliminates the need for large microstrip matching components. The novel amplifier obtains greater than 10-dB gain over a DC-5 GHz band, a maximum IP3 of 27 dBm, and a minimum noise figure of 3.7 dB. In comparison with a HBT-only Darlington feedback design, the employment of the CG HEMT results in a 6-dB improvement in IP3 and a 1.5-2 dB reduction in noise figure. By adjusting the common-gate HEMT bias, the input return-loss can be tuned for near ideal 50 /spl Omega/ match (>20 dB). The actively matched HEMT-HBT amplifier demonstrates an active circuit technique, which can reduce the chip area and cost of HEMT-HBT MMICs while improving their performance.

Optical amplifier noise-figure reduction using avariable polarisation beam splitter

A 3 dB noise figure (NF) reduction of an Er3+-doped fibre amplifier (EDFA) has been experimentally demonstrated using a variable polarisation beam splitter (VPBS). A VPBS controlled by two liquid crystal cells adequately separates half the amplified spontaneous emission (ASE) power of the optical output signal from the optical amplifier and reduces the NF by up to 3 dB. This technique is verified in an EDFA with a measured NF reduction of 3 dB. It yields an EDFA with an NF of 1.2–1.7 dB and gain of 32–34 dB over a wide spectral bandwidth.